I am not in marketing or PR, but in addition to being a reader, I also am an editor and an aspiring author who watches the trends and, luckily, has a friend who works in the social media field, so I can follow her lead and pick her brain when needed.
Here is a quick list of things for newbie indie authors to consider as they self-market their books:
Twitter and Facebook -- Create accounts under your pen name and post regularly.
Scheduling -- If you have a full-time job and/or a family, posting two to three times a day can be hard to manage. Instead, find a platform, such as HooteSuite or TweetDeck, that allows you to sit down for half an hour once every week or two to schedule your minimum, standard posts. This gives you a social media presence even when you can't log in.
Political and social issues -- Before posting on a political or social issue, be sure it is something you believe in strongly enough to lose readers and followers. I strongly suggest having a personal account and a pen name account; use your personal account for political, social and, well, personal interactions. While writing is a calling, it is also a business; keep the personal and business separate. Your real life friends will probably also thank you.
Monitor @replies and DMs -- Interact with your followers. If all you do is post and never reply, you look like a social media bot -- a machine or an intern could do it, and followers can tell! They want to interact with you.
80/20 -- You are marketing your books, so people will expect you to post about your books, but keep in mind that if all you post about is that your book is available, well-- it will be BORING. Make sure at least 20% of your posts not about your book, but about your likes or dislikes, your writing life and books you read, or other things that make you a real and interesting person who might write something the rest of us will want to read.
Pinterest, Instagram, GetGlue, and other social media sites -- Keep an eye on new social media trends. This can be done by following other people, noting what other sites they are using to post on Twitter and Facebook. A lot of these sites can be connected to Twitter and FB, so you can incorporate (aka, schedule) posts about your hobbies and interests using other sites.
Pinterest example: If you LOVE shoes, browse for shoes on Pinterest and schedule Tweets about shoes (which will help you with your 20% personal posts-- kill two birds with one stone). Or, connect your Pinterest account to your Twitter account so you can easily Tweet something you are Pinning (a Pinterest feature).
GetGlue example: Checking into GetGlue (after connecting it to your Twitter account) when you watch a movie or tv show gives followers a chance to get to know your entertainment tastes...something they can easily reply to you about.
Sharing the love -- Repost positive, non self-promotional reviews of other authors' books. The authors of those books are more likely to share your posts (and increase your following) and can also help you build an on-line community. In addition, if followers consider you a source for good recommendations, they are more likely to at look at your own books.
Blogs and reviews -- If you post blogs or book review on your website, don't just Tweet about to those blogs and reviews; repost Tweets/links to those blogs and reviews a few times a month (especially your favorite ones). Use your scheduler! This will increase your following and increase visits to your website.
Freebies -- I'm gonna be honest and admit that I don't think freebies of one book will increase sales of your other books.
Booksellers put restrictions on freebies, which means the author loses control over pricing and other issues.
Offering your book for free on Amazon or other bookseller sites will definitely attract deal seekers. For newbies, I feel like people will read your free book but won't review it or buy your other books. Aren't you offering a free book as a means of gaining readers and followers? Chicken or the egg...situation...
If you have a good following and book readership, freebies might help sales of your other books...might.
Talk to a real marketer with experience with ebook freebies.
Giveaways -- Contrary to my opinion on freebies, I do think giveaways are good. Giveaways allow you to control what you give away (with no conditions from book sellers), how much you give away, and what conditions you want to put on giving it away. Ebook giveaways are easy because Amazon and B&N both allow someone to "gift" a book if you have the recipient's email address. Note: You will have to buy that book you are giving away.
The quick giveaway -- On the spur of the moment, an author can post something like; "First person to @reply XXXX get's a free ebook copy of YYY". Quick, easy to administer, and normally a positive response.
Review -- An author can give away a book to one person on the condition that the recipient actually reviews the book on Goodreads or a bookseller's website.
WRITE! -- Don't let social media take over your life. Be smart and disciplined. Twitter and FB can be time-suckers, so don't let them take away from your writing time!
Social media is constantly evolving and changing, so what we do today could change tomorrow.